Sorry cannot see the pictures, but it sounds like a bad case of Pear Scab to me. The shop man was right. Remove any damaged leaves and burn or bin them. Do not put them on the compost heap. Then do the thumnail test. Scratch the bark on a branch, if the underneath is green then the branch is still alive. If all the branches are dead ie no green then go back to the G/C and ask for replacement trees. Otherwise soak the tree with a systemic fungicide, not sure what is available now as we do not use them. You do not really need to water again if there are no leaves, the tree will just get sodden roots which will do it no good.
It may regrow leaves now or it might just wait until spring, hard to know. Hope they do survive for you.